linux/include/linux/ksm.h
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   1#ifndef __LINUX_KSM_H
   2#define __LINUX_KSM_H
   3/*
   4 * Memory merging support.
   5 *
   6 * This code enables dynamic sharing of identical pages found in different
   7 * memory areas, even if they are not shared by fork().
   8 */
   9
  10#include <linux/bitops.h>
  11#include <linux/mm.h>
  12#include <linux/pagemap.h>
  13#include <linux/rmap.h>
  14#include <linux/sched.h>
  15
  16struct stable_node;
  17struct mem_cgroup;
  18
  19#ifdef CONFIG_KSM
  20int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
  21                unsigned long end, int advice, unsigned long *vm_flags);
  22int __ksm_enter(struct mm_struct *mm);
  23void __ksm_exit(struct mm_struct *mm);
  24
  25static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
  26{
  27        if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags))
  28                return __ksm_enter(mm);
  29        return 0;
  30}
  31
  32static inline void ksm_exit(struct mm_struct *mm)
  33{
  34        if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
  35                __ksm_exit(mm);
  36}
  37
  38/*
  39 * A KSM page is one of those write-protected "shared pages" or "merged pages"
  40 * which KSM maps into multiple mms, wherever identical anonymous page content
  41 * is found in VM_MERGEABLE vmas.  It's a PageAnon page, pointing not to any
  42 * anon_vma, but to that page's node of the stable tree.
  43 */
  44static inline int PageKsm(struct page *page)
  45{
  46        return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) ==
  47                                (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM);
  48}
  49
  50static inline struct stable_node *page_stable_node(struct page *page)
  51{
  52        return PageKsm(page) ? page_rmapping(page) : NULL;
  53}
  54
  55static inline void set_page_stable_node(struct page *page,
  56                                        struct stable_node *stable_node)
  57{
  58        page->mapping = (void *)stable_node +
  59                                (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM);
  60}
  61
  62/*
  63 * When do_swap_page() first faults in from swap what used to be a KSM page,
  64 * no problem, it will be assigned to this vma's anon_vma; but thereafter,
  65 * it might be faulted into a different anon_vma (or perhaps to a different
  66 * offset in the same anon_vma).  do_swap_page() cannot do all the locking
  67 * needed to reconstitute a cross-anon_vma KSM page: for now it has to make
  68 * a copy, and leave remerging the pages to a later pass of ksmd.
  69 *
  70 * We'd like to make this conditional on vma->vm_flags & VM_MERGEABLE,
  71 * but what if the vma was unmerged while the page was swapped out?
  72 */
  73struct page *ksm_might_need_to_copy(struct page *page,
  74                        struct vm_area_struct *vma, unsigned long address);
  75
  76int page_referenced_ksm(struct page *page,
  77                        struct mem_cgroup *memcg, unsigned long *vm_flags);
  78int try_to_unmap_ksm(struct page *page, enum ttu_flags flags);
  79int rmap_walk_ksm(struct page *page, int (*rmap_one)(struct page *,
  80                  struct vm_area_struct *, unsigned long, void *), void *arg);
  81void ksm_migrate_page(struct page *newpage, struct page *oldpage);
  82
  83#else  /* !CONFIG_KSM */
  84
  85static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
  86{
  87        return 0;
  88}
  89
  90static inline void ksm_exit(struct mm_struct *mm)
  91{
  92}
  93
  94static inline int PageKsm(struct page *page)
  95{
  96        return 0;
  97}
  98
  99#ifdef CONFIG_MMU
 100static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
 101                unsigned long end, int advice, unsigned long *vm_flags)
 102{
 103        return 0;
 104}
 105
 106static inline struct page *ksm_might_need_to_copy(struct page *page,
 107                        struct vm_area_struct *vma, unsigned long address)
 108{
 109        return page;
 110}
 111
 112static inline int page_referenced_ksm(struct page *page,
 113                        struct mem_cgroup *memcg, unsigned long *vm_flags)
 114{
 115        return 0;
 116}
 117
 118static inline int try_to_unmap_ksm(struct page *page, enum ttu_flags flags)
 119{
 120        return 0;
 121}
 122
 123static inline int rmap_walk_ksm(struct page *page, int (*rmap_one)(struct page*,
 124                struct vm_area_struct *, unsigned long, void *), void *arg)
 125{
 126        return 0;
 127}
 128
 129static inline void ksm_migrate_page(struct page *newpage, struct page *oldpage)
 130{
 131}
 132#endif /* CONFIG_MMU */
 133#endif /* !CONFIG_KSM */
 134
 135#endif /* __LINUX_KSM_H */
 136
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